Genomic integrity is crucial for an organism's survival. Surveillance mechanisms ensure that the genome is properly replicated and faithfully transmitted from a cell to its daughters. If the integrity of the genome is compromised, a checkpoint mechanism is activated to delay cell cycle progression until the aberration is repaired. In particular, the DNA replication checkpoint delays progression into mitosis until the DNA has been accurately and fully replicated. While some components of the checkpoint mechanism are known, many of the elements involved in the events underlying the checkpoint response have not been characterized or are not fully understood. Using an in vitro expression cloning strategy (IVEC) to screen a Xenopus oocyte cDNA library, we wish to identify novel components and interactions involved in the DNA replication checkpoint to provide a better understanding of this vital process. [unreadable] [unreadable]